The present invention relates generally to slow-motion systems in apparatuses for reproducing rotary recording mediums. More particularly, the invention relates to an apparatuse of the type for reproducing, from a rotary recording medium on which signals have been recorded along a spiral track, the signals by means of a reproducing transducer, in which apparatus one and the same track turn is repeatedly reproduced a plural number of times by the reproducing transducer, and thereafter the reproducing transducer is shifted to the adjacent track turn to repeatedly reproduce a plural number of times thereby to obtain a slowmotion reproduced picture. More specifically, the invention relates to a system for reproducing the picture with minimal oscillation thereof in this slow-motion reproduction.
A new information signal recording and/or reproducing system has been proposed in a U.S. Pat. application Ser. No. 785,095 entitled "INFORMATION SIGNAL RECORDING SYSTEM" filed Apr. 6, 1977, now U.S. Pat. No. 4,331,976, of which the assignee is the same as that of the present application. According to this proposed system, the recording system forms pits in accordance with the information signal being recorded along a spiral track on a flat disc shaped recording medium (hereinafter referred to as disc), without forming a groove therein. In this reproducing system, a reproducing stylus traces over along this track thereby to reproduce the recorded information signal in response to variations in the electrostatic capacitance.
In this system, since a groove for guiding the reproducing stylus is not provided on the disc, pilot or reference signals should be recorded on or in the vicinity of a track of the information signal, such as a video signal, on the disc. Upon reproduction, the reference signals are reproduced together with the video signal. Tracking servo control is carried out so that the reproducing stylus accurately traces along the track in response to the reproduced reference signals.
By the use of this previously proposed system, there is no possibility whatsoever of the reproducing stylus or the disc being damaged since the recording track has no groove. The stylus can trace the same portion of the track repeatedly many times, whereby a special reproduction such as still, slow motion, or quick motion reproduction becomes possible.
Thus, in a U.S. Pat. application Ser. No. 4,813 entitled "SPECIAL REPRODUCING SYSTEM IN AN APPARATUS FOR REPRODUCING VIDEO SIGNALS FROM A ROTARY RECORDING MEDIUM" filed Jan. 19, 1979, now U.S. Pat. No. 4,340,907, of which the assignee is the same as that of the present application, a special reproducing system in a disc reproducing apparatus was proposed which is capable of performing a special reproduction in which a picture having a motion different from the upon normal reproduction is obtained in an excellent manner.
The special reproducing system comprises a reproducing element for tracing the track of the disc and picking up the recorded signal, a tracking control mechanism for operating in response to skip pulses applied thereto to cause the reproducing element to shift to an adjacent track turn of the spiral track thereby to undergo skipping, and a skip pulse generating circuit for generating skip pulses with timings corresponding to the vertical blanking period positions of the recorded video signal, where the skip pulses are of a number corresponding to an operational mode for carrying out a special reproduction differing from normal reproduction at every rotational period of the rotary recording medium, and supplying the skip pulses to the tracking control mechanism. The reproducing element is skipped to an adjacent track turn within the vertical blanking period of the recorded video signal, by the tracking control mechanism responsive to the skip pulses.
Accordingly, the noise introduced when the reproducing element moves to an adjacent track does not appear in the picture, and a special reproduction such as still reproduction, slow-motion and quick-motion reproduction in the forward direction, and normal-speed, slow-motion, and quick-motion reproduction in the backward direction can be performed in which a fine picture is obtained.
A standard specification wherein a video signal corresponding to two frames, that is, four fields, is recorded ordinarily for one track turn (the portion of the spiral track corresponding to one revolution of the recording disc) is established by conditions for practical use such as the quantity of recording on the disc, the rotational speed of the disc, and the diameter of the disc. By repeating the operation of repeatedly reproducing n times, by means of the special reproducing system of the above mentioned proposal, one and the same track turn of a disc recorded in conformance with this standard specification, shifting to the adjacent track turn after thus reproducing, and again repeatedly reproducing this adjacent track turn n times, a reproduced picture of slow motion of n times can be obtained.
However, when slow-motion reproduction by means of the special reproducing system of the above mentioned proposal of a disc on which a video signal corresponding to two frames is recorded on each track turn is carried out in this manner, the information contents (pictures) of two different frames are alternately superposed and give rise to an oscillation of the picture.